Roof Rafter Dimensions

Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

Roof rafter dimensions.

Half building width minus 1 2 ridge thickness. Rafter run outer wall this should be measured starting from the center of the roof span and then extending to the very edge of the exterior wall. Next set the framing square on top of the rafter beam and use a pencil to trace the outside edge of the framing square s tongue. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak.

This diagram illustrates the typical arrangement of a rafter and purlin roof and shows the dimensions referred to in the tables above. Usually 400 450 or 600mm but any value can be used up to 610mm max. Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter. Allow for ridge thickness when determining rafter run to outer wall.

There are several variables to consider when determining the proper rafter size. Once you ve marked the lines use your pencil to draw the diagonal length on the rafter. Here the number is 941 86 inches. For example if the roof rises 4 feet and the span is 16 feet twice the run then the pitch is 4 16 or 1 4.

Here the number is 1166 66 inches. Gable walls need to be strapped to the roof at the maximum 2m centres using 30 x 5m galvanised mild steel straps. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. The rafter member will be longer.

If you plan to have overhang etc. Find its length with our online rafter length calculator. Rafter is the beam supporting the building. Are there any brittle finishes e g.

To cut roof rafters start by fixing the stair gauges on your framing square to the dimensions of your pitch. This is the distance between rafter centres. Plasterboard on the underside of the rafter. Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof.

Pitch is the incline of the roof represented as the ratio of rise to the span twice the run. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. It is the length of this portion of the rafter. Imposed loads roof snow load and short term point load.

Print full scale rafter cut templates and birdsmouth templates fold template over rafter to mark or cut through.